Rain Alarm API V2 🌧️

A simple PHP-based rain radar API that provides current rain radar information based on GPS coordinates.

The API accepts latitude and longitude values and returns radar information as JSON. It is designed for easy integration with Home Assistant REST sensors, IoT systems, and automation platforms.

Features

• 🌍 Coordinate-based rain radar lookup
• 🌧️ Current rain detection
• 📡 Radar reflectivity data (dBZ)
• 💧 Rain intensity values
• 🏠 Native Home Assistant REST sensor support
• ⚡ Lightweight JSON API

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API Usage

Endpoint

GET https://your-domain.com/rainAlarm/{latitude}/{longitude}

Example:

https://your-domain.com/rainAlarm/46.0100237/14.3693499

Where:

Parameter	Description
latitude	GPS latitude
longitude	GPS longitude

Example location:

Latitude: 46.0100237
Longitude: 14.3693499

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API Response

The API returns JSON data.

Example:

{
  "data": {
    "rain": true,
    "severety": 2,
    "dbz": 35,
    "rr_val": 1.8,
    "lastUpdate": "2026-07-21T12:00:00"
  }
}

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JSON Fields

Field	Type	Description
rain	boolean	Indicates if rain is detected
severety	number	Rain severity level
dbz	number	Radar reflectivity value
rr_val	number	Rain rate estimation
lastUpdate	string	Time of last radar update

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Home Assistant Integration

Add the following REST sensor to your configuration.yaml:

sensor:
  - platform: rest
    name: Rain Sensor
    resource: https://your-domain.com/rainAlarm/46.0100237/14.3693499
    method: GET
    timeout: 20

    value_template: >
      {% if value_json is defined and value_json.data is defined %}
        {{ value_json.data.dbz }}
      {% else %}
        unknown
      {% endif %}

    json_attributes_path: $.data
    json_attributes:
      - rain
      - severety
      - dbz
      - rr_val
      - lastUpdate

    scan_interval: 300

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Home Assistant Sensor Output

The sensor state will contain the radar dbz value:

Example:

sensor.rain_sensor = 35

Attributes:

rain: true
severety: 2
dbz: 35
rr_val: 1.8
lastUpdate: "2026-07-21T12:00:00"

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Rain Detection Binary Sensor

Create a binary sensor based on the API rain value:

template:
  - binary_sensor:
      - name: Rain Detected
        device_class: moisture
        state: >
          {{ state_attr('sensor.rain_sensor', 'rain') == true }}

Result:

ON  = Rain detected
OFF = No rain

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Example Automation

Send a notification when rain starts:

automation:
  - alias: Rain Alert
    trigger:
      - platform: state
        entity_id: binary_sensor.rain_detected
        to: "on"

    action:
      - service: notify.mobile_app_your_phone
        data:
          message: "Rain detected by radar."

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Update Interval

Radar information normally changes every few minutes.

Recommended polling interval:

scan_interval: 300

This means Home Assistant updates the sensor every 5 minutes.

For faster alerts:

scan_interval: 120

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Testing the API

You can test the API using:

curl https://your-domain.com/rainAlarm/46.0100237/14.3693499

Expected response:

{
  "data": {
    "rain": false,
    "severety": 0,
    "dbz": 0,
    "rr_val": 0,
    "lastUpdate": "2026-07-21T12:00:00"
  }
}

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Troubleshooting

Home Assistant shows unknown

Check:

• The API URL is reachable
• The JSON response is valid
• The response contains the data object
• Your server allows external requests

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API returns empty data

Verify:

• Latitude and longitude are valid
• Radar provider data is available
• The API server has internet access

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Possible Automations

This API can be used for:

• 🌧️ Rain notifications
• 🪟 Automatic window closing
• 🌱 Smart irrigation control
• 🏡 Outdoor lighting automation
• 🚗 Garage door protection
• ☀️ Weather dashboards

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License

Use according to the license included in this repository.